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Eclipse Magnitude and Obscuration
The
eclipse
magnitude is defined as the fraction of the Sun's
diameter occulted by the Moon, and the eclipse obscuration as
the fraction of the Sun's surface area occulted by the Moon. The
area
covered
by the the moon can easily be computed: The area of the segment is: The secant P_{1}P_{2} is at: and the angles are:
Diameters:
d_{Moon}/d_{Sun}= 1.1 (total eclipse)
Diameters:
d_{Moon}/d_{Sun}= 0.9 (annular eclipse)
Diameters:
d_{Moon}/d_{Sun}= 0.9, 1.0, and 1,1
Select
Data from the menu to get this window:
Magnitudes of Solar Eclipses 2006  2010 (Fred Espeneak):

Calculating the area of the Sun covered during an eclipse 
(c) 20062008 J. Giesen
Modified: 2010, Mar 07